1. Field of the Invention
The present invention relates to an option setting circuit for a system configuration and, more particularly, to an automatic option setting circuit for a device with a re-writable memory.
2. Discussion of the Related Art
Devices used in, for example, an IBM PC(Personal Computer) environment are assigned a memory address region, input/output address region, interrupt types to be used, or DMA (Direct Memory Access) channels based in part on options set in a configuration control register. The option settings, which are set before starting an operation, control operating characteristics of the device.
In the methods for setting those options, there is, a first, hardware based, method which selectively applies 5V or 0V to achieve a preset value using a jumper (i.e., dip-switch). The 5V or 0V is defined in advance and the preset value determines an option. Options set according to this hardware method are maintained whether the system is on or off. In addition, there is, a second, software based, method which modifies a configuration control register. In this method the options for modifying the control register have been defined by a program after the system is booted. An option selected in the software method requires an access to the configuration control register every time a user boots the system. Currently, many devices employ the two methods.
A conventional option setting circuit will be explained with reference to the attached drawings. FIG. 1 is a block diagram of a system of a conventional option setting circuit.
The configuration control register 3 assigns resources, such as address regions, interrupt types to be used, DMA(Direct Memory Access) channels, and other options for a device in, for example, an IBM PC environment. As shown in FIG. 1, some of the options of the configuration control register can be set by means of a hardware jumper (i.e., dip-switch). The system of the conventional option setting circuit includes a PC interfacing part 1 for connecting the option setting circuit to a main system in the PC environment, a register access logic part 2 connected to the PC interfacing part 1 and having address/data bus lines for accessing a configuration control register 3, which has options to be selected defined therein, and a jumper 4 connected to a portion of the configuration control register 3 for applying 5V or 0V at the moment of power on start-up to set an option defined in the configuration register 3.
When a user desires to change the options set in the aforementioned conventional option setting circuit, a value set in the jumper 4 has to be adjusted manually before turning on the system. A different method of setting options in the configuration control register, instead of the hardware jumper method, is by means of a software program. When using a software program option setting method, the configuration control register needs to be accessed through particular input/output address regions. When it is intended to modify a set option, the program needs to be executed to access the configuration control register 3. When options are set by a software program, the last option settings are placed in a file to be automatically read-in without intervention by the user every time the PC is turned on, thereby setting the options. Consequently, the software program option setting involves using the PC processing unit to access the configuration control register.
However, conventional option setting techniques have the following problems.
First, the method of setting options through the hardware jumper method has the inconvenience that the system has be turned off to adjust the settings and then turned on to use the adjusted settings, and the user must manually operate the hardware (e.g., jumper or dip-switch) to adjust the option settings.
Second, the method of setting options by means of a software program has the inconvenience that, because options are reset when the computer is turned off, a software program has to log any modifications to the option settings in a program file and reload them every time the system is turned on. That is, the software program has to access the control register every time the computer is turned to reload the option settings which requires extra processing by the PC processing unit.